I believe that the not shooting is part of the reloading. [Bows have a reload time before being able to shoot again]I'm not sure it's a bug, it's probably intended but I would like to make sure if it's not.
When you shoot the Fire Bow (not sure if it happens to Stun and Confusion Bows as well) repeatedly, it ceases to create Fire or even shoot.
But yeah, it often does not create fire on the ground, can be frustrating.